A typical system for enabling multiple entities to exchanging data or communicate with one another may include a form of a distributed communication system, in which multiple parties to a communication are connected to each other through a network and a central hub or switch. In many circumstances, where that data being exchanged includes sensitive information, it is important to maintain privacy from external security threats. Additionally, in some circumstances, the network itself may not be reliably secure or trustworthy. For example, various parties engaging in a teleconference may be speaking about sensitive information from various trusted locations throughout the world, but the telecommunication system or the central data mixer used to transmit data between the parties may not be secure or trustworthy.
A vocoder or voice encoder is a device that reproduces speech/voice. A vocoder may include both an encoder for encoding the voice data and a decoder for decoding the encoded voice data. In the encoder, the input is passed through a multiband filter, each band is passed through an envelope follower, and the control signals from the envelope followers are communicated to the decoder. The decoder applies these (amplitude) control signals to corresponding filters in the synthesizer. By encrypting the control signals, voice transmission can be secured against interception.
However, conventional vocoders have not been all of linear, computationally efficient and compatible with additive homomorphic encryption schemes to enabled encrypted VoIP teleconferencing capabilities.